Reduction Roadmaps: Methods of determining limit-values for climate impact in construction

Paper in proceeding, 2025

Legal and organisational limit-values for the climate impact of new buildings have emerged as an important tool to transition new construction toward emissions levels acceptable with regards to the ecological planetary boundaries while remaining feasible in terms of social needs and economic restraints. However, since no agreed-upon methods for defining the limit-values exist, organisations have developed their own bespoke methodologies, making limit-values difficult to compare directly. Decision-making may thus be conducted based on methodologies lacking scientific rigour. The aim of the present work is to compare the approaches in terms of proposed methodologies and resulting limit-values. Specifically, the objective was to identify key methodological choices which need to be made in order to establish a comparable limit-value. In a review of 14 approaches in Nordic countries, including legislative and industrial initiatives, 27 such key methodological choices were identified and organised into a conceptual framework. The initiatives were characterised as applying bottom-up or top-down approaches to define limit-values. Bottom-up approaches based on available technologies generally allow more emissions than top-down approaches based on carbon budgets, indicating a need for harmonisation and hybrid approaches. The findings can support actors in harmonising approaches and help initiatives benchmark their stated limitvalues. Finally, knowledge gaps related to important methodological choices when establishing limit-values for the environmental impact of new construction are identified.